This invention relates to a device for picking up tissues from a body cavity, which is used in combination with an endoscope.
As shown in FIG. 1, a known tissue picking-up device comprises an outer sheath 1 constituted by a coiled metal wire element, an extension wire 2 extending through the outer sheath 1, a tissue picking-up section 4 connected to one end of the wire 2 by a connector 5, and a holding section 6 for holding the other end of the wire 2. To pick up desired tissues or cells from a body cavity it is necessary to move the tissue picking-up section 4 for a small distance. Since the section 4 is moved by moving the outer sheath 1, a relative movement must not occur between the sheath 1 and the section 4. To avoid such a relative movement, the wire 2 is strongly pulled toward the holding section 6 and held by the holding section 6 so that the connector 5 always abuts on the distal end of the outer sheath 1.
Let it be assumed that the metal wire constituting the outer sheath 1 and the extension wire 2 be each made of a rigid body but can be flexed. When the outer sheath 1 is bent as shown in FIG. 2, that portion of the outer sheath 1 which is adjacent to its center of curvature does not substantially shrink lengthwise thereof. But, since the extension wire 2 is connected to the holding section 6 and the connector 5 abutting against the distal end of the outer sheath 1, the wire 2 must be elongated, depending on how much the outer sheath 1 is bent.
In practice, some clearance is provided between the adjacent turns of the coil constituting the sheath 1. The turns can be elastically deformed to some extent, and the wire 2 can be elastically elongated to some degree due to the fact that the coiled metal wire element and the extension wire are not completely rigid bodies. The outer sheath 1 can, therefore, be bent but to a limited extent. When the sheath 1 is bent beyond the limited extent, however, the wire 2 would be cut or be broken at the connector 5 or slip off the holding section 6.
While it is inserted into a meandering body cavity, an endoscope is often bent very much and so is its forceps channel. There is a reverse possibility that the known device as illustrated in FIG. 1 cannot be inserted into the forceps channel which is bent too much. Moreover, if the outer sheath 1 is bent and the wire 2 is cut in a body cavity, a part of the cut wire 2, the tissue picking-up section 4 and the connector 5 may fall into the body cavity from the endoscope and adversely remain in the body cavity.